best way to use dosing pump

Steve, I use same as you; seachem reef builder line. So I guess pH will go slightly up.

Mag, I'm thinking about putting it as an ATO until I get my float switches fixed and then wired properly.
It won't be perfect but I feel like it will at least help with top offs

 

Dingo

I got my Alk and Ca dosing down to pretty accurate consistency by dosing these Nightly and Daily respectively

but my Mag
despite having Tropic Marin, Red Sea and Salifert test kits I could not see a significant result in test differences over the course of any 1 week
I seemed to stay between 1410 and 1440 - so some of the deviations could be user error rather than an indication of true demand
I ended up just doing what your suggesting doing -dosing once per week for Magnesium half a dozen teaspoons in 1 litre of warmed RODI

Steve